Vaporetto lecoaspira Red warning light and audible beep come on.

\015 I have a vaporetto lecoaspira 710 which is just back from being repaired. We can’t find the manual at home and have been looking at the instructions on line for the 700 / 701 as it seems to be the same machine. I have filled the tank, put the water up to max in the bucket you lift out, set the pressure gauge to 3. The green light comes on and I push the button to start the boiler and then the warning beep comes and the red ‘square’ lights up which means the water isn’t getting to the boiler. Can anyone tell me what I am doing wrong please.\015 – Polti Eco Pro 3000 Canister Steam Vacuum